1. Field of the Invention
The invention is a continuous process for preparing modified succinimides. These modified succinimides are used as dispersants in lubricating oils for internal combustion engines.
2. Description of Methods in the Field of the Invention
Internal combustion engines operate under a wide range of temperatures including low temperature stop-and-go service as well as high temperature conditions produced by continuous high speed driving. Stop-and-go driving, particularly during cold, damp weather conditions, leads to the formation of a sludge in the crankcase and in the oil passages of a gasoline or a diesel engine. This sludge seriously limits the ability of the crankcase oil to effectively lubricate the engine. In addition, the sludge with its entrapped water tends to contribute to rust formation in the engine. These problems tend to be aggravated by the manufacturer's lubrication service recommendations which specify extended oil drain intervals.
It is known to employ nitrogen containing dispersants and/or detergents in the formulation of crankcase lubricating oil compositions. Many of the known dispersant/detergent compounds are based on the reaction of an alkenylsuccinic acid or anhydride with an amine or polyamine to produce an alkylsuccinimide or an alkenylsuccinamic acid a determined by selected conditions of reaction.
T. J. Karol et al. U.S. Pat. No. 4,482,464 teaches hydrocarbyl-substituted mono- and bis- succinimides comprising a polyamine chain linking hydroxyacyl radicals. These compositions are compounded with a mineral oil to produce a lubricant composition.
T. E. Nalesnik U.S. Pat. No. 4,636,322 teaches Mannich phenol coupled glycamide bis-alkenyl succinimides. These compounds are synthesized step wise in a batch process. The compounds are effective as dispersants when incorporated in a minor proportion in lubricating oil.
T. E. Nalesnik et al U.S. Pat. No. 4,713,189 teaches a lubricating oil dispersant prepared by coupling two polyethyleneamine moieties with an aldehyde and a phenol, followed by conversion to a succinimide. The resulting coupled succinimide is then acylated with glycolic acid to form a glycolated Mannich phenol coupled mono-alkenyl succinimide. These dispersants are synthesized stepwise in a batch process.
R. H. Wollenberg et al U.S. Pat. Nos. 4,612,132 and 4,747,965 teach modified polyamino alkenyl and alkyl succinimides. These compounds are prepared by a continuous process. According to the continuous process, an alkenyl or alkyl succinic anhydride is contacted with a polyamine to form a polyamino alkenyl or alky succinimide. This composition is contacted with a cyclic carbonate to form the modified polyamino alkenyl or alkyl succinimide. Water is removed from the reaction system either before or during the course of the reaction via azeotroping or distillation.